Radio Frequency Identification (RFID) systems have become common in commercial environments, such as a retail store for example. In a typical scenario, RFID reader energy is typically set at the maximum allowed effective isotropic radiated power (EIRP) to achieve the greatest penetration into shopping carts or other containers. This allows the RFID reader to read the greatest amount of RFID tags at the greatest range. However, there are some cases where it is desired to read RFID tags only within a specified read area without reading other RFID tags that may be near the specified read area.
For example, it may be desired to read all the items that are leaving the store, which can be useful for inventory management. In this case, RFID readers can be stationed at the store exit, with their associated antennas pointed into the area of interest, i.e. the store exit. This arrangement achieves robust RFID reads of the RFID tags leaving the store through the area of interest, although spillover into adjacent areas is usually a problem, where items that are near the exit, but not actually leaving the store, are accidentally read by the RFID reader. This results in an ambiguity of what actually passed through the intended read area. Even with careful antenna placement to avoid illuminating areas adjacent to the store exit, the reflections produced by people walking through the intended read area can cause unintentional energy to spill into non-read zones.
Similarly, it could be that other RFID readers that are being used near the exit in the store for normal stock maintenance could accidentally read RFID tags that are leaving the store, which will result in an inaccuracy of stock inventory in the store.
Accordingly, there is a need for a definitive technique to define a read area to record RFID tags passing through the defined read area, without capturing those RFID tags that are only near the read area but not passing through the read area. In the prior art this could be achieved by jamming the nearby tags or readers. However, jamming will not allow nearby tags to be read at all, which will prevent proper inventory management. Therefore, it would also be of benefit if those nearby tags adjacent to the defined read area could be properly read by other RFID readers in the normal course of business.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.